In automotive vehicles it is common practice to cool the engine by pumping hot engine coolant through a radiator hose to a radiator which dissipates heat to ambient air and then returning the coolant through another radiator hose. Such radiators have efficient metallic tube and fin structures for transmitting heat to the air, and reservoirs or tanks for coupling the coolant between the radiator hoses and the tubes. The tanks may be metal but polymeric materials have become increasingly more common in usage.
In many cases the engine lubricating oil or the transmission oil also is cooled. A variety of cooling practices have been used such as separate heat exchangers for the oil or some combination of the oil and coolant heat exchange function. Many vehicles employ an oil cooler which resides within the radiator tank to effect heat transfer from the oil to the engine coolant. The size and complexity of the latter type of oil cooler varies according to the required thermal capacity but, in general, they are brazed assemblies built up of tubes and fins having inlet and outlet fittings extending through the radiator tank. Such structures have many parts and are thus expensive to manufacture, and they increase the size and complexity of the radiator tank.
It is already known, as shown for example in U.S. Pat. No. 4,545,334 to Nakagawa et al, to use in-line oil coolers comprising concentric metal pipes. In that patent the cooler structure is rigid, not conformable to radiator hose routings. The structure comprises many parts, including a triple-walled pipe structure, separate fins within the pipes and separate nipples attached to the pipes, apparently welded together.